Inhibition of the Voltage-Gated Sodium Current and Opening of Nanopores By Ultra -Short Electric Pulses

Abstract

Exposure of mammalian cells to high-voltage, ultra-short electric pulses (USEP) leads to formation of membrane nanopores and alters multiple physiological processes, including function of voltage-gated channels. However, it is not known if USEP affect the channels directly, or the effects are mediated by leak currents through nanopores and respective shifts in the transmembrane ion balance. We employed whole-cell patch-clamp to explore the effect of 300-ns USEP on voltage-gated sodium channels in neuroblastoma cells (NG108). We found that a single USEP could inhibit VG INa , with the threshold at about 1.8 kV/cm. Voltage-dependent activation and inactivation curves shifted to more negative membrane potentials: V0.5 of activation moved from −22.8±0.2mV before USEP to −26.4±0.6mV after it (mean ± s.e.), and V0.5 of inactivation changed from −65.9±0.2mV to −72.2±0.2, respectively; the slope factor did not change. Concurrently, USEP exposures induced a non-inactivating, voltage-sensitive inward current due to nanopore formation. The presence of 100μM Gd3+ in the bath buffer significantly reduced the nanopore current and also eliminated the inhibitory effect of USEP on VG INa. This finding suggests that USEP-induced inhibition of VG INa. and changes in its kinetic characteristics may be mediated by opening of nanopores and consequent alterations of the ion equilibrium.Supported by NIH (NCI) R01CA125482.